With the intelligent development of projector applications, requirements for imaging clarity of a projector are increasing. A projector body projects a projection picture to a screen or a wall through a projection lens, and it is necessary to adjust a projection focusing device to focus the projection lens when a projection distance changes.
At present, a smart terminal with a projection function adjusts a projection focal distance in automatic focusing manners. Herein, in one manner, it refers to: projecting an image to a screen, capturing the image through a camera, re-converting the collected image into a digital image signal by an image collection chip, and processing the image; and moving a position of a motor to perform scanning, calculating image clarity evaluation values of different positions, and taking a position with the highest image clarity evaluation value as an optimum position. According to this manner, once the motor is moved, it is necessary to capture and process an image after waiting for stabilization of the motor and an image synchronization signal. Thus, only one image is captured for each frame, and since scanning is required, a focusing speed is low. Under extreme situations, it is even necessary to scan the whole motor range (the motor is located at the vertex of one end, and the optimum position is located at the vertex of another end). Moreover, after focusing, an image also has a certain probability of being not clear.
In another manner, it refers to: after measuring a distance between a screen and a projection by using an additional ranging device, driving a motor according to a relationship between the distance and the focal distance, and moving a projection lens to a specified position. Although this manner is simple, an imaging clarity detection device is not adopted, so that errors between individuals cannot be solved.